The purpose of the invention is to propose a device that integrates with a system that transforms a message into a plurality of cells, also called a `celluliser`, and that makes it possible to space the transmissions of cells from one another over time, by a predetermined duration.
A plurality of messages is stored in a memory called message memory, and each one of them is provided so as to be sent at a preset time and in a pre-set direction. With each message there is associated a virtual communication circuit to which a virtual circuit number is ascribed, and hereafter indicated as VCI and, to each virtual circuit there corresponds a delivery of cells that is negotiated by a protocol, of the type named FRP in the field of technique.
The problem that arises is to supply a periodic time reference for the sending of the cells belonging to a same message. As the rate of flow ascribed to each virtual circuit precisely depends on this virtual circuit and consequently on its VCI number, as well as on the FRP negotiation, the periods associated with each message will be different. It is therefore necessary periodically to awaken the sending of the cells of a given message while keeping track of the entire group of messages.
The purpose of the present invention therefore is to propose a spacing device that makes it possible to solve this problem and that, to that end, is responsible for supplying the awakening clock-times to a managing unit the main function of which is to govern the sending of a given cell pertaining to a given message, at a time set by the spacing device.
There are already known devices that are based on the use of a plurality of counters independent from one another, one counter being ascribed to a given message. The overflow of a counter governs the sending of a cell of the corresponding message. These devices may become costly when the number of messages to be treated is high. Moreover, they require solving the problem of conflicts that may arise when several countersoverflow within the same time interval.
There are also known devices that make use of counters, as do the preceding ones, but the latter are executed by means of a memory provided to store counting values associated with messages, and of adders provided to update, at each sending of a cell of a given message, the counting value associated with that message. There also, however, a high number of messages implies the use of a memory with a high number of storing blocks, and difficulty in incrementing all of the blocks at the appropriate time. Moreover, the overflow of each counting value is difficult to check.
The present invention therefore is proposing a process to space cells over time, that makes it possible to solve the different problems indicated heretofore.